Dynamic network allocation for mobile router

ABSTRACT

Methods and apparatus for implementing a Home Agent supporting Mobile IP and being capable of allocating one or more networks to a mobile router which registers with the Home Agent comprise receiving a registration request packet from the mobile router, the registration request packet indicating one or more networks being requested by the mobile router from the Home Agent. The one or more networks are allocated to the mobile router corresponding to the one or more networks being requested by the mobile router from the Home Agent. A registration reply packet identifying the one or more networks allocated to the mobile router is then sent to the mobile router.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.09/746,409 filed Dec. 20, 2000 now U.S. Pat. No. 6,959,341, naming KentK. Leung as inventor, and entitled, “DYNAMIC NETWORK ALLOCATION FORMOBILE ROUTER,” which is incorporated herein by reference for allpurposes.

This application is also related to U.S. patent application Ser. No.09/227,396, naming Kent K. Leung as inventor, and entitled “MOBILE IPMOBILE ROUTER,” which is incorporated herein by reference in itsentirety and for all purposes.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to Mobile IP network technology. Moreparticularly, the present invention relates to dynamic networkallocation for a Mobile IP mobile router.

2. Description of the Related Art

Mobile IP is a protocol which allows laptop computers or other mobilecomputer units (referred to as “Mobile Nodes” herein) to roam betweenvarious sub-networks at various locations—while maintaining internetand/or WAN connectivity. Without Mobile IP or related protocol, a MobileNode would be unable to stay connected while roaming through varioussub-networks. This is because the IP address required for any node tocommunicate over the internet is location specific. Each IP address hasa field that specifies the particular sub-network on which the noderesides. If a user desires to take a computer which is normally attachedto one node and roam with it so that it passes through differentsub-networks, it cannot use its home base IP address. As a result, abusiness person traveling across the country cannot merely roam with hisor her computer across geographically disparate network segments orwireless nodes while remaining connected over the internet. This is notan acceptable state-of-affairs in the age of portable computationaldevices.

To address this problem, the Mobile IP protocol has been developed andimplemented. An implementation of Mobile IP is described in RFC 2002 ofthe Network Working Group, C. Perkins, Ed., October 1996. Mobile IP isalso described in the text “Mobile IP Unplugged” by J. Solomon, PrenticeHall. Both of these references are incorporated herein by reference intheir entireties and for all purposes.

The Mobile IP process and environment are illustrated in FIG. 1. Asshown there, a Mobile IP environment 2 includes the internet (or a WAN)4 over which a Mobile Node 6 can communicate remotely via mediation by aHome Agent 8 and a Foreign Agent 10. Typically, the Home Agent andForeign Agent are routers or other network connection devices performingappropriate Mobile IP functions as implemented by software, hardware,and/or firmware. A particular Mobile Node (e.g., a laptop computer)plugged into its home network segment connects with the internet throughits designated Home Agent. When the Mobile Node roams, it communicatesvia the internet through an available Foreign Agent. Presumably, thereare many Foreign Agents available at geographically disparate locationsto allow wide spread internet connection via the Mobile IP protocol.Note that it is also possible for the Mobile Node to register directlywith its Home Agent.

As shown in FIG. 1, Mobile Node 6 normally resides on (or is “based at”)a network segment 12 which allows its network entities to communicateover the internet 4 through Home Agent 8 (an appropriately configuredrouter denoted R2). Note that Home Agent 8 need not directly connect tothe internet. For example, as shown in FIG. 1, it may be connectedthrough another router (a router R1 in this case). Router R1 may, inturn, connect one or more other routers (e.g., a router R3) with theinternet.

Now, suppose that Mobile Node 6 is removed from its home base networksegment 12 and roams to a remote network segment 14. Network segment 14may include various other nodes such as a PC 16. The nodes on networksegment 14 communicate with the internet through a router which doublesas Foreign Agent 10. Mobile Node 6 may identify Foreign Agent 10 throughvarious solicitations and advertisements which form part of the MobileIP protocol. When Mobile Node 6 engages with network segment 14, ForeignAgent 10 relays a registration request to Home Agent 8 (as indicated bythe dotted line “Registration”). The Home and Foreign Agents may thennegotiate the conditions of the Mobile Node's attachment to ForeignAgent 10. For example, the attachment may be limited to a period oftime, such as two hours. When the negotiation is successfully completed,Home Agent 8 updates an internal “mobility binding table” whichspecifies the care-of address (e.g., a collocated care-of address or theForeign Agent's IP address) in association with the identity of MobileNode 6. Further, the Foreign Agent 10 updates an internal “visitortable” which specifies the Mobile Node address, Home Agent address, etc.In effect, the Mobile Node's home base IP address (associated withsegment 12) has been shifted to the Foreign Agent's IP address(associated with segment 14).

Now, suppose that Mobile Node 6 wishes to send a message to acorresponding node 18 from its new location. A message from the MobileNode is then packetized and forwarded through Foreign Agent 10 over theinternet 4 and to corresponding node 18 (as indicated by the dotted line“packet from MN”) according to a standard internet protocol. Ifcorresponding node 18 wishes to send a message to Mobile Node—whether inreply to a message from the Mobile Node or for any other reason—itaddresses that message to the IP address of Mobile Node 6 on sub-network12. The packets of that message are then forwarded over the internet 4and to router R1 and ultimately to Home Agent 8 as indicated by thedotted line (“packet to MN(1)”). From its mobility binding table, HomeAgent 8 recognizes that Mobile Node 6 is no longer attached to networksegment 12. It then encapsulates the packets from corresponding node 18(which are addressed to Mobile Node 6 on network segment 12) accordingto a Mobile IP protocol and forwards these encapsulated packets to a“care of” address for Mobile Node 6 as shown by the dotted line (“packetto MN(2)”). The care-of address may be, for example, the IP address ofForeign Agent 10. Foreign Agent 10 then strips the encapsulation andforwards the message to Mobile Node 6 on sub-network 14. The packetforwarding mechanism implemented by the Home and Foreign Agents is oftenreferred to as “tunneling.”

In addition to providing connectivity to a mobile node, it may bedesirable to provide for the mobility of one or more networks movingtogether, such as on an airplane or a ship. RFC 2002 section 4.5discusses the possibility of implementing mobile routers.

In one approach suggested in RFC 2002 section 4.5, a Home Agent isconfigured to have a permanent registration for each fixed node. Forinstance, a mobile router may support multiple nodes which may be fixedwith respect to the mobile router. In order to receive communicationfrom a corresponding node, messages must be routed to the appropriatefixed node. As the RFC suggests, a Home Agent may be configured to havea permanent registration for each fixed node. By way of example, thepermanent registration may indicate the mobile router's address as thecare-of address. Thus, a separate mapping table may associate the IPaddress of each of the fixed nodes with the mobile router. However, thisis problematic since the mapping table is typically configured while themobile router is coupled to the Home Agent. In other words, the routingtable is static. Suppose a person boards an airplane and wishes toconnect a laptop to the airplane's “mobile network” via the mobilerouter. If a new node is added to the mobile router after the airplaneleaves the airport, the IP address of this new node may not be added tothe mapping table. As a result, communication cannot be received by thisnew node via the mobile router. In addition, since the mobile router 20may accommodate thousands of devices, or nodes, there would potentiallybe an enormous number of entries to store in such a mapping table forthese nodes. Moreover, such a mapping table may include entries formultiple mobile routers. Accordingly, such a mapping table would consumea substantial amount of memory as well as be cumbersome to search.

FIG. 2 is a block diagram illustrating a system in which a mobile routeris implemented. As shown, when a mobile router 202 roams to a firstForeign Agent 204, it registers with its Home Agent 206 so that it mayreceive packets from a corresponding node 208. When the mobile router202 subsequently roams to a second Foreign Agent 210, it again registerswith its Home Agent 206. In this manner, a device 212 that has connectedto the mobile router 202 may communicate via the internet 4 byconnecting to a network 214 of the mobile router 202.

Address space is a precious resource. For mobile routers which have oneor more associated networks, address space is consumed even more quicklythan for individual nodes. More particularly, IP addresses for entirenetworks rather than single nodes must be allocated. According tocurrent mobile router implementation schemes, the Home Agent isconfigured with those networks that are connected to the mobile router.Thus, address space is typically allocated statically for entirenetworks.

An airplane is an exemplary scenario in which a mobile router may beimplemented. For instance, each plane may have a mobile router (andtherefore many networks) on board to provide Internet connectivity andservices. Statically allocating address space to these networks is anefficient mechanism for configuring the Home Agent with the informationit needs to forward messages to a mobile router supported by the HomeAgent. However, since not all planes may be active (i.e., flying)simultaneously, it would be beneficial to only allocate subnets toactive planes.

In view of the above, it would be desirable to have improved techniquesfor implementing network allocation for a Mobile IP mobile router.

SUMMARY OF THE INVENTION

The present invention enables networks to be allocated dynamically to amobile router. This is accomplished, in part, through a request for oneor more networks from the mobile router. Thus, networks are allocatedonly to active routers. In this manner, address space is conserved.

In accordance with one aspect of the invention, a Home Agent isconfigured to allocate one or more networks to a mobile router thatregisters with the Home Agent. To initiate the allocation process, aregistration request packet is received from the mobile router. Theregistration request packet indicates one or more networks beingrequested by the mobile router from the Home Agent. The one or morenetworks are allocated to the mobile router corresponding to the one ormore networks being requested by the mobile router from the Home Agent.A registration reply packet identifying the one or more networksallocated to the mobile router is then sent to the mobile router.

In accordance with another aspect of the invention, a mobile router isconfigured to request one or more networks from a Home Agent duringregistration. The mobile router composes a registration request packetindicating one or more networks being requested by the mobile routerfrom a Home Agent. The registration request packet is sent to the HomeAgent. A registration reply packet identifying one or more networksallocated to the mobile router by the Home Agent is then received by themobile router. The mobile router may then configure its interfaces withIP addresses selected from the allocated networks.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of a Mobile IP network segment and associatedenvironment.

FIG. 2 is a system diagram illustrating a system in which a mobilerouter is implemented.

FIG. 3A is a diagram illustrating an exemplary registration request thatmay be sent in accordance with one embodiment of the invention.

FIG. 3B is a diagram illustrating an exemplary registration reply thatmay be sent by the Home Agent in accordance with one embodiment of theinvention.

FIG. 4 is a process flow diagram illustrating one method of dynamicnetwork allocation during registration of a mobile router in accordancewith one embodiment of the invention.

FIG. 5 is a process flow diagram illustrating one method of deallocatingnetworks during deregistration of a mobile router in accordance with oneembodiment of the invention.

FIG. 6 is a process flow diagram illustrating one method of deallocatingnetworks when a lifetime of the mobile router has expired in accordancewith one embodiment of the invention.

FIG. 7 is a block diagram of a network device that may be configured toimplement aspects of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, numerous specific details are set forth inorder to provide a thorough understanding of the present invention. Itwill be apparent, however, to one skilled in the art, that the presentinvention may be practiced without some or all of these specificdetails. In other instances, well known process steps have not beendescribed in detail in order not to unnecessarily obscure the presentinvention.

The present invention enables dynamic network allocation anddeallocation. More particularly, in accordance with one embodiment, thisis accomplished through a network allocation extension to theregistration request packet. FIG. 3A is a diagram illustrating anexemplary registration request that may be sent in accordance with oneembodiment of the invention. As shown, a registration request packet 302includes a network allocation extension 304 indicating one or morenetworks being requested by the mobile router from the Home Agent. Moreparticularly, in the network allocation extension 304, the mobile routermay optionally indicate a number of subnets 306 being requested by themobile router. In addition, the network allocation extension 304 mayalso include a size 308 of the one or more networks being requested bythe mobile router from the Home Agent. For instance, the mobile routermay separately indicate a number of networks and a size of each of thenetworks requested. Alternatively, the mobile router may merely indicatea size or subnet mask for each network. In other words, the mobilerouter may specify three sizes, therefore implying that three networksare requested. Similarly, the mobile router may specify a single size,which may be divided into multiple networks.

When the requested address space has been allocated for use by themobile router, the Home Agent sends a registration reply packetidentifying the allocated networks. FIG. 3B is a diagram illustrating anexemplary registration reply that may be sent by the Home Agent inaccordance with one embodiment of the invention. As shown, aregistration reply packet 310 that includes a network allocationextension 312 identifying the one or more networks 314 that have beenallocated to the mobile router.

FIG. 4 is a process flow diagram illustrating one method of dynamicnetwork allocation during registration of a mobile router in accordancewith one embodiment of the invention. As shown at block 402, when amobile router roams to (or detects) a Foreign Agent, it composes andsends a registration request packet to its Home Agent. As describedabove, the registration request packet includes a network allocationextension. When the Home Agent receives the registration request packet,it allocates the one or more networks to the mobile router correspondingto the network allocation extension of the registration request packetat block 404. More particularly, the Home Agent obtains the informationfrom the network allocation extension (e.g., subnet sizes) and allocatesthe appropriate network(s) from a pool of available networks. Forinstance, the pool may be a local pool that is managed by the HomeAgent.

Rather than requiring the Home Agent to manage the pool of availablenetworks, the pool of available networks may be managed by a server thatis external to the Home Agent. For instance, a class of servers known as“AAA” or triple-A servers may be employed. The AAA representsauthentication, authorization, and accounting. While authenticationdetermines “who” an entity is, authorization determines what services auser is allowed to perform, or access. Various protocols such as theRemote Authentication Dial In User Service (RADIUS) and TACACS+ may beimplemented to provide such a server. RFC 2138 describes the RADIUSProtocol and is hereby incorporated by reference. Similarly, RFC 1492describes TACACS and the Internet-Draft “The TACACS+ Protocol Version1.78,” available athttp://www.ietf.org/internet-drafts/draft-grant-tacacs-02.txt, describesTACACS+. Both of these documents are incorporated herein by referencefor all purposes.

Alternatively, a DHCP (Dynamic Host Configuration Protocol) server maybe employed. DHCP is a protocol that lets network administrators managecentrally and automate the assignment of Internet Protocol (IP)addresses in an organization's network. DHCP uses the concept of a“lease” or amount of time that a given IP address will be valid for acomputer. The lease time can vary depending on how long a mobile routeror user is likely to require the Internet connection at a particularlocation. Using very short leases, DHCP can dynamically reconfigurenetworks in which there are more computers than there are available IPaddresses. Once the networks have been allocated to the mobile router,the Home Agent adds the subnet(s) to a routing table at block 406. Moreparticularly, the routing table is updated to include one or moreentries for the one or more networks that are allocated to the mobilerouter. Each entry in the routing table includes a care-of addressassociated with the one or more networks. For instance, each entry mayinclude a network IP address, a next hop router IP address to thecare-of address for the network, and an interface. In addition toupdating the routing table, the Home Agent also creates a tunnel betweenthe Home Agent and the mobile router. In addition, it creates a bindingentry in the Mobility Binding Table to enable the Home Agent to identifythe current location (e.g., Foreign Agent) to which the mobile routerhas roamed. More particularly, the Home Agent updates the MobilityBinding Table to associate the mobile router with a care-of address.

When the Home Agent has determined that registration of the mobilerouter is accepted, the Home Agent composes and sends a registrationreply packet including a network allocation extension identifying theallocated subnet(s) at block 408. When the mobile router receives theregistration reply packet identifying one or more networks allocated toit by the Home Agent, it processes the network allocation extension atblock 410. More particularly, the mobile router selects from the one ormore allocated networks an IP address and configures an interface of themobile router with the IP address such that a network coupled to theinterface is identified by the IP address. In addition, the mobilerouter adds the networks identified in the network allocation extensionto a private DHCP pool available to the mobile router at block 412,thereby enabling the mobile router to manage networks allocated to it.At block 414, the mobile router also creates a tunnel to the Home Agentso that it can receive tunneled packets and updates its registrationtable to indicate a lifetime granted during registration of the mobilerouter with the Home Agent.

When the networks are no longer used by the mobile router, they aredeallocated. Deallocation of allocated networks may occur in twoinstances. First, deallocation may occur upon deregistration of themobile router with the Home Agent. Second, deallocation may occur whenthe lifetime of the mobile router expires.

FIG. 5 is a process flow diagram illustrating one method of deallocatingnetworks during deregistration of a mobile router in accordance with oneembodiment of the invention. At block 502, the mobile router sends aderegistration request to the Home Agent. The Home Agent receives thederegistration request at block 504 and deallocates the subnetsassociated with the mobile router at block 506. For instance, thisdeallocation process may involve replacing the networks to a pool ofavailable networks. The Home Agent then completes the deregistrationprocess at block 508 by updating the Mobility Binding Table to removethe association between the mobile router and the care-of address. Inaddition, the appropriate entries and/or networks are removed from therouting table, deleting the tunnel to the mobile router, and deletingthe appropriate networks. The Home Agent then sends a deregistrationreply to the mobile router to indicate that deregistration of the mobilerouter is complete as shown at block 510.

When the mobile router receives the deregistration reply at block 512,it removes the one or more networks previously allocated to it from itsprivate DHCP pool at block 514. In addition, it deconfigures theappropriate interfaces so that they will no longer be identified by thepreviously configured IP addresses at block 516. At block 518 the mobilerouter deletes the tunnel to the Home Agent and updates its registrationtable to delete the appropriate entry from its registration table.

As described above, a second way in which deallocation of networksallocated to the mobile router may be performed is automatically whenthe lifetime of the mobile router has expired. FIG. 6 is a process flowdiagram illustrating one method of deallocating networks when a lifetimeof the mobile router has expired in accordance with one embodiment ofthe invention. When the lifetime of the mobile router has expired (e.g.,the mobility binding table entry is deleted upon expiration of thespecified lifetime) at block 602, the Home Agent and the mobile routerperform substantially the same functions as described above withreference to FIG. 5 describing the functions performed uponderegistration of the mobile router. Thus, at block 604, the Home Agentdeallocates the networks associated with the mobile router by replacingthe networks to a pool of available networks. In addition, the HomeAgent deletes the appropriate Mobility Binding Table entry, deletes thetunnel between the mobile router and the Home Agent, and deletes theappropriate networks or entries from the routing table at block 606. Themobile router similarly removes the appropriate networks from itsprivate DHCP pool at block 608 and deconfigures the previously allocatednetworks from its interface(s) at block 610. At block 612, the mobilerouter deletes the tunnel between the mobile router and the Home Agentas well as the appropriate registration entry from its registrationtable.

The present invention enables networks to be allocated dynamically to amobile router during the registration process. As a result, networksneed not be allocated statically to the mobile router. Moreover, addressspace is conserved since networks are only allocated to “active” mobilerouters.

It is important to note that each AAA server implemented for purposes ofmanaging a pool of available networks may provide conventionalauthentication and accounting services as well as authorizationservices. RADIUS and TACACS+ conventionally provide authentication,authorization, and accounting services. Thus, these protocols are wellsuited for the servers of the present invention. However, the inventionis not limited to these protocols. Other authentication, authorization,and accounting protocols may be used.

The invention can also be embodied as computer readable code on acomputer readable medium. The computer readable medium is any datastorage device that can store data which can thereafter be read by acomputer system. Examples of the computer readable medium includeread-only memory, random-access memory, CD-ROMs, magnetic tape, andoptical data storage devices.

The apparatus (Home Agent or Foreign Agent) of this invention may bespecially constructed for the required purposes, or may be a generalpurpose programmable machine selectively activated or reconfigured by acomputer program stored in memory. The processes presented herein arenot inherently related to any particular router or other apparatus. In apreferred embodiment, any of the Home and Foreign Agents of thisinvention may be specially configured routers such as speciallyconfigured router models 2500, 2600, 3600, 4000, 4500, 4700, 7200, and7500 available from Cisco Systems, Inc. of San Jose, Calif.. A generalstructure for some of these machines will appear from the descriptiongiven below.

Generally, the registration technique of the present invention may beimplemented on software and/or hardware. For example, it can beimplemented in an operating system kernel, in a separate user process,in a library package bound into network applications, on a speciallyconstructed machine, or on a network interface card. In a specificembodiment of this invention, the technique of the present invention isimplemented in software such as an operating system or in an applicationrunning on an operating system.

A software or software/hardware hybrid registration system of thisinvention is preferably implemented on a general-purpose programmablemachine selectively activated or reconfigured by a computer programstored in memory. Such programmable machine may be a network devicedesigned to handle network traffic. Such network devices typically havemultiple network interfaces including frame relay and ISDN interfaces,for example. Specific examples of such network devices include routersand switches. For example, the registration systems of this inventionmay be specially configured routers such as specially configured routermodels 1600, 2500, 2600, 3600, 4500, 4700, 7200, 7500, and 12000available from Cisco Systems, Inc. of San Jose, Calif. A generalarchitecture for some of these machines will appear from the descriptiongiven below. In an alternative embodiment, the registration system maybe implemented on a general-purpose network host machine such as apersonal computer or workstation. Further, the invention may be at leastpartially implemented on a card (e.g., an interface card) for a networkdevice or a general-purpose computing device.

Referring now to FIG. 7, a router 1110 suitable for implementing thepresent invention includes a master central processing unit (CPU) 1162,interfaces 1168, and a bus 1115 (e.g., a PCI bus). When acting under thecontrol of appropriate software or firmware, the CPU 1162 is responsiblefor such router tasks as routing table computations and networkmanagement. It may also be responsible for updating mobility binding andvisitor tables, etc. It preferably accomplishes all these functionsunder the control of software including an operating system (e.g., theInternetwork Operating System (IOS®) of Cisco Systems, Inc.) and anyappropriate applications software. CPU 1162 may include one or moreprocessors 1163 such as a processor from the Motorola family ofmicroprocessors or the MIPS family of microprocessors. In an alternativeembodiment, processor 1163 is specially designed hardware forcontrolling the operations of router 1110. In a specific embodiment, amemory 1161 (such as non-volatile RAM and/or ROM) also forms part of CPU1162. However, there are many different ways in which memory could becoupled to the system.

The interfaces 1168 are typically provided as interface cards (sometimesreferred to as “line cards”). Generally, they control the sending andreceiving of data packets over the network and sometimes support otherperipherals used with the router 1110. Among the interfaces that may beprovided are Ethernet interfaces, frame relay interfaces, cableinterfaces, DSL interfaces, token ring interfaces, and the like. Inaddition, various very high-speed interfaces may be provided such asfast Ethernet interfaces, Gigabit Ethernet interfaces, ATM interfaces,HSSI interfaces, POS interfaces, FDDI interfaces and the like.Generally, these interfaces may include ports appropriate forcommunication with the appropriate media. In some cases, they may alsoinclude an independent processor and, in some instances, volatile RAM.The independent processors may control such communications intensivetasks as packet switching, media control and management. By providingseparate processors for the communications intensive tasks, theseinterfaces allow the master microprocessor 1162 to efficiently performrouting computations, network diagnostics, security functions, etc.

Although the system shown in FIG. 7 is one specific router of thepresent invention, it is by no means the only router architecture onwhich the present invention can be implemented. For example, anarchitecture having a single processor that handles communications aswell as routing computations, etc. is often used. Further, other typesof interfaces and media could also be used with the router.

Regardless of network device's configuration, it may employ one or morememories or memory modules (including memory 1161) configured to storeprogram instructions for the general-purpose network operations andmechanisms for registration and routing functions described herein. Theprogram instructions may control the operation of an operating systemand/or one or more applications, for example. The memory or memories mayalso be configured to store tables such as mobility binding andregistration tables, etc.

Because such information and program instructions may be employed toimplement the systems/methods described herein, the present inventionrelates to machine readable media that include program instructions,state information, etc. for performing various operations describedherein. Examples of machine-readable media include, but are not limitedto, magnetic media such as hard disks, floppy disks, and magnetic tape;optical media such as CD-ROM disks; magneto-optical media such asfloptical disks; and hardware devices that are specially configured tostore and perform program instructions, such as read-only memory devices(ROM) and random access memory (RAM). The invention may also be embodiedin a carrier wave travelling over an appropriate medium such asairwaves, optical lines, electric lines, etc. Examples of programinstructions include both machine code, such as produced by a compiler,and files containing higher level code that may be executed by thecomputer using an interpreter.

Although illustrative embodiments and applications of this invention areshown and described herein, many variations and modifications arepossible which remain within the concept, scope, and spirit of theinvention, and these variations would become clear to those of ordinaryskill in the art after perusal of this application. For instance,although the specification has described routers, other entities used totunnel packets to nodes on remote network segments can be used as well.For example, bridges or other less intelligent packet switches may alsoemploy the standby protocol of this invention. Accordingly, the presentembodiments are to be considered as illustrative and not restrictive,and the invention is not to be limited to the details given herein, butmay be modified within the scope and equivalents of the appended claims.

1. A mobile router supporting Mobile IP and being capable of requestingone or more networks during registration with a Home Agent, the mobilerouter comprising: a processor; and a memory, at least one of theprocessor and the memory being adapted for: composing a registrationrequest packet, the registration request packet indicating one or morenetworks being requested by the mobile router from the Home Agent;sending the registration request packet to the Home Agent; receiving aregistration reply packet from the Home Agent, the registration replyidentifying one or more networks allocated to the mobile router by theHome Agent; and adding the one or more networks to a private DHCP poolavailable to the mobile router.
 2. The mobile router as recited in claim1, wherein the registration request packet indicates a number of subnetsbeing requested by the mobile router.
 3. The mobile router as recited inclaim 1, wherein the registration request packet indicates a size of theone or more networks being requested by the mobile router from the HomeAgent.
 4. The mobile router as recited in claim 1, wherein at least oneof the processor and the memory are further adapted for: detecting aForeign Agent prior to composing and sending the registration requestpacket to the Home Agent.
 5. The mobile router as recited in claim 1, atleast one of the processor and the memory being adapted for: selectingfrom the one or more networks allocated to the mobile router by the HomeAgent an IP address; and configuring an interface of the mobile routerwith the IP address such that a network coupled to the interface isidentified by the IP address.
 6. The mobile router as recited in claim5, wherein at least one of the processor and the memory are furtheradapted for: deconfiguring the interface of the mobile router such thatthe interface is not identified by the IP address.
 7. The mobile routeras recited in claim 6, wherein deconfiguring the interface is performedwhen a lifetime of the mobile router has expired.
 8. The mobile routeras recited in claim 6, wherein at least one of the processor and thememory are further adapted for: sending a deregistration request to theHome Agent prior to deconfiguring the interface of the mobile router. 9.The mobile router as recited in claim 1, wherein at least one of theprocessor and the memory are further adapted for: removing the one ormore networks from the private DHCP pool available to the mobile router.10. The mobile router as recited in claim 9, wherein removing the one ormore networks from the private DHCP pool available to the mobile routeris performed when a lifetime of the mobile router has expired.
 11. Themobile router as recited in claim 9, wherein at least one of theprocessor and the memory are further adapted for: sending aderegistration request to the Home Agent prior to removing the one ormore networks from the private DHCP pool available to the mobile router.12. The mobile router as recited in claim 1, wherein at least one of theprocessor and the memory are further adapted for: updating aregistration table to indicate a lifetime granted during registration ofthe mobile router with the Home Agent.
 13. The mobile router as recitedin claim 12, wherein at least one of the processor and the memory arefurther adapted for: deleting an entry from the registration table whenthe lifetime has expired.
 14. The mobile router as recited in claim 1,at least one of the processor and the memory being further adapted for:sending a deregistration request to the Home Agent.
 15. The mobilerouter as recited in claim 14, wherein at least one of the processor andthe memory are further adapted for: receiving a deregistration replyfrom the Home Agent.
 16. The mobile router as recited in claim 1,wherein each of the networks allocated to the mobile router includesmore than one address.
 17. The mobile router as recited in claim 16,wherein each of the networks being requested by the mobile routerincludes more than one address.
 18. The mobile router as recited inclaim 2, wherein each of the networks being requested by the mobilerouter includes more than one address.
 19. In a mobile router supportingMobile IP, a method of requesting one or more networks duringregistration with a Home Agent, comprising: composing a registrationrequest packet, the registration request packet indicating one or morenetworks being requested by the mobile router from a Home Agent; sendingthe registration request packet to the Home Agent; receiving aregistration reply packet from the Home Agent, the registration replyidentifying one or more networks allocated to the mobile router by theHome Agent; and adding the one or more networks to a private DHCP poolavailable to the mobile router.
 20. The method as recited in claim 19,wherein the registration request packet indicates a number of subnetsbeing requested by the mobile router.
 21. The method as recited in claim19, wherein the registration request packet indicates a size of the oneor more networks being requested by the mobile router from the HomeAgent.
 22. The method as recited in claim 19, further comprisingdetecting a Foreign Agent prior to composing and sending theregistration request packet to the Home Agent.
 23. The method as recitedin claim 19, further comprising: selecting from the one or more networksallocated to the mobile router by the Home Agent an IP address; andconfiguring an interface of the mobile router with the IP address suchthat a network coupled to the interface is identified by the IP address.24. The method as recited in claim 23, further comprising: deconfiguringthe interface of the mobile router such that the interface is notidentified by the IP address.
 25. The method as recited in claim 24,wherein deconfiguring the interface is performed when a lifetime of themobile router has expired.
 26. The method as recited in claim 24,further comprising: sending a deregistration request to the Home Agentprior to deconfiguring the interface of the mobile router.
 27. Themethod as recited in claim 19, further comprising: removing the one ormore networks from the private DHCP pool available to the mobile router.28. The method as recited in claim 27, wherein removing the one or morenetworks from the private DHCP pool available to the mobile router isperformed when a lifetime of the mobile router has expired.
 29. Themethod as recited in claim 27, further comprising: sending aderegistration request to the Home Agent prior to removing the one ormore networks from the private DHCP pool available to the mobile router.30. The method as recited in claim 19, further comprising: updating aregistration table to indicate a lifetime granted during registration ofthe mobile router with the Home Agent.
 31. The method as recited inclaim 30, further comprising: deleting an entry from the registrationtable when the lifetime has expired.
 32. The method as recited in claim19, further comprising: sending a deregistration request to the HomeAgent.
 33. The method as recited in claim 32, further comprising:receiving a deregistration reply from the Home Agent.
 34. The method asrecited in claim 19, wherein each of the networks allocated to themobile router includes more than one address.
 35. The method as recitedin claim 19, wherein each of the networks being requested by the mobilerouter includes more than one address.
 36. A mobile router supportingMobile IP and adapted for requesting one or more networks duringregistration with a Home Agent, comprising: means for composing aregistration request packet, the registration request packet indicatingone or more networks being requested by the mobile router from a HomeAgent; means for sending the registration request packet to the HomeAgent; means for receiving a registration reply packet from the HomeAgent, the registration reply identifying one or more networks allocatedto the mobile router by the Home Agent; and means for adding the one ormore networks to a private DHCP pool available to the mobile router.